IR spectroscopy measurements may be useful for a variety of purposes including aerospace, automotive and industrial applications, as well as biological and biomedical applications. For example, infrared (IR) radiation is readily absorbed by materials in association with relative motions (vibrations) of atoms such as carbon, hydrogen, oxygen and nitrogen. As such, IR spectroscopy measurements may indicate a condition of a wide variety of organic as well as inorganic materials.
For example, frequently it is necessary to determine the thickness of a coating material on a substrate, to verify that the film coating thickness is sufficiently thick and/or to verify that the film has the proper composition, including but not limited to, bond primer film thicknesses on a metallic substrate.
IR spectroscopy methods are relatively easy for measurement of contamination on metals, but are difficult for measurement of contamination on dielectric coatings and composite substrates. A conventional method of determining contamination on surface coatings (and composites) may involve performing a hexane extraction of the suspected contaminated area. The hexane solvent and any materials extracted by the solvent may be transferred to a gold cup. After complete evaporation of the solvent, the silicon which remains in the cup may be measured using a bench-top spectrometer. However, this method may be laborious and time-consuming and not applicable to real-time field measurements of contaminants on surface coatings.
Therefore, a method for determining surface contamination of materials using non-destructive Mid-IR spectroscopy which enables real-time field measurement of contamination on coatings and non-metallic substrates (composites) in manufacturing and repair situations is needed.